Tuesday, September 17, 2013
Salmon and agriculture in the Delta region
"Knaggs Ranch: Growing rice and salmon on a floodplain"
2013-09-17 upload by "UC Davis Center for Watershed Sciences" [http://www.youtube.com/watch?v=dT5Vffdnwb8]:
Researchers with the UC Davis Center for Watershed Sciences are working with a consortium of private landowners, conservation groups and public agencies to create more habitat for struggling Central Valley salmon populations. Their experiments on the Yolo Bypass in Yolo County indicate that parts of the 59,000-acre agricultural floodway could make a productive salmon nursery at relatively little cost to farmers. Young salmon stocked on seasonally flooded rice fields grew much faster and fatter than those left in the Sacramento River, earning them the name "floodplain fatties." The Experimental Agricultural Floodplain Pilot Study began in 2011 and is scheduled to continue through 2014.
"For salmon and rice to thrive in Yolo Bypass, 'just add water'"
2013-10-25 by KAT KERLIN from "UC Davis News Service"
Created: 10/25/2013 09:28:33 AM PDT
rom a fish-eye view, rice fields in California's Yolo Bypass provide an all-you-can-eat bug buffet for juvenile salmon seeking nourishment on their journey to the sea.
That's according to a new report detailing the scientific findings of an experiment that planted fish in harvested rice fields earlier this year, resulting in the fattest, fastest-growing salmon on record in the state's rivers.
The report, provided to the U.S. Bureau of Reclamation, describes three concurrent studies from researchers at the UC Davis nonprofit California Trout and the California Department of Water Resources.
The scientists investigated whether rice fields on the floodplain of Yolo Bypass could be managed to help recover California's populations of chinook salmon, and if so, the ideal habitats and management approaches that could allow both fish and farms to thrive.
"We're finding that land managers and regulatory agencies can use these agricultural fields to mimic natural processes," said co-author Carson Jeffres, field and laboratory director of the Center for Watershed Sciences at UCD. "We still have some things to learn, but this report is a big step in understanding that."
Researchers found that the fish did not have a preference among the three rice field types tested: stubble, plowed and fallow. The food supply was so plentiful that salmon had high growth rates across habitats and management methods.
"It's like a dehydrated food web," said Jeffres of the harvested rice fields. "Just add water. All of those habitats are very productive for fish."
The salmon did demonstrate a preference for habitats with better water flow. Jeffres compared it to choosing among three good restaurants: Each offers good food with hearty portions, but one has better ambience and so is chosen above the others. In this case, the better water flow was the ambience the fish preferred.
Among the key findings:
* Experimental flooding of Yolo Bypass rice fields during the winter can create productive aquatic food webs for salmon.
* Average growth rates during the study's 41 days were the highest recorded in fresh water in California. Growth of juvenile chinook averaged 0.93 mm per day, with growth of 1.5 mm per day observed during specific two-week intervals.
* Mortality was greater than in the team's previous 2012 study at Knaggs Ranch. In the 2013 study, between 0 and 29 percent of free-swimming fish survived, while 35 to 98 percent of fish in enclosures survived.
* Lower survival rates were attributed to bird predation. The winter of 2013, when the study was conducted, was one of the driest on record in the Sacramento Valley, which may have drawn more birds to the inundated rice fields, and to the fish. The study plots were also relatively shallow, providing little escape for fish. A follow-up study planned for 2014 will explore the role of depth as a refuge for fish against avian predators.
* Fish reared in plowed rice fields grew faster than those reared over stubble or weedy vegetation. However, all habitat types were beneficial to the fish, suggesting farm managers may have more flexibility in land treatment after harvest.
"Chinook salmon thrive in flooded-field experiment"
2013-10-25 by David Perlman from " San Francisco Chronicle" [http://www.sfgate.com/science/article/Chinook-salmon-thrive-in-flooded-field-experiment-4924225.php]:
Researchers who fattened young chinook salmon in flooded fields after the rice harvest last winter reported Thursday that the fish grew fast and to record sizes, offering a promising new way to improve survival of the long-threatened salmon.
As youngsters, those rare but delectable fish of the Sacramento River swim to the ocean each spring and reach adulthood there before returning to spawn in the river's tributaries.
But each year, predators kill millions of the young fish as they reach the sea because the fish are too small and helpless to escape.
Now researchers report that an experiment begun in April shows how those juvenile fish can grow faster and fatter in rice fields that are regularly flooded along the river than they do in the open water of the river.
"I can see the potential that millions and millions of young salmon, growing in flooded fields along the Sacramento, could be given a better chance to survive when they reach the ocean," said Jacob Katz, the biologist who led the research.
The experiment's results were detailed in a report to the Bureau of Reclamation by Carson Jeffres, laboratory director of the UC Davis Center for Watershed Science, and Katz, regional manager of CalTrout, a fisheries conservation organization. The two agencies partnered for the experiment in the second year of an effort to reverse the long and devastating population decline of the salmon.
Jeffres said the experiment involved three different plots of farmland totaling 18 acres on the floodplain of the Yolo Bypass near Sacramento that were flooded with water after the rice was harvested.
"It was like a dehydrated food web," Jeffres said of those fields. "You just add water, and all the habitats proved really productive for the fish."
Four thousand young trout were placed in the flooded plots of a rice ranch along the Yolo Bypass, which is used to divert water from the Sacramento River to protect Sacramento from flooding.
One flooded plot had been left with a bottom of rice stubble after the rice was harvested; another had been turned into bare ground; and the bottom of the third was allowed to hold natural weeds.
The young fish in all three fields grew swiftly, Katz said. But the bottomland that was bare before it was flooded quickly became a much richer source of highly nutritious plankton for the young salmon than the other two fields, he said.
The survival rate for all young salmon was lower than expected, Katz said. Last winter's drought, he said, dried land around the fields for miles around and birds searching for the nearest water found the rice fields, he said.
"We really got hammered by birds," Katz said. "They found plenty of food on our fields." Despite that problem, the average growth rate of the surviving chinook was higher than ever recorded in the river, Katz and Jeffres said.
"It's a win-win model that can be replicated around the state," Katz said.
Next year, he said, another experiment will cover more than 2,500 acres of flooded rice fields after the crop has been harvested.
The Bureau of Reclamation contributed $150,000 to the research and a combination of other agencies - including CalTrout and the Knaggs ranch where the experiment was conducted - contributed to the $500,000 total, he said.